Okay.
Some details about this study:
* 18 participants:
* 3 men and 15 women
* each could type at least 55 wpm
* none with any history of RSI
* age range from 18–49, average 33.5
* typing experience range 6–32 years, average 16 years
* Study was 5 consecutive days of typing
* Half the participants used a wrist rest, half did not
* Participants had chairs with adjustable height and armrests
* Researchers adjusted chairs/table for standard posture across participants
* No mention of how far away the keyboards were from the body, or how the typists were sitting in their chairs
* Standard keyboard was white Alps, split keyboard looks like MX keycaps from the picture
* The two keyboards had different amounts of front/back tilt, but they placed them both with the home row at the same height
* First day, typing test on flat keyboard, various setup, a couple hours experience with the split keyboard
* three days, 4 one-hour typing sessions with 10m breaks between
* one day with the flat keyboard and two days with the split keyboard in fixed configuration
* different participants got different orders
* last day, they could configure the split keyboard however they wanted, but no data was recorded
* Posture was judged by researchers looking at a 3-minute video of typing and assigning numerical scores for different posture features like various wrist angles, etc. For wrist pronation, they scored palms parallel to table = 4 (substantial pronation) and palms perpendicular to table = 0 (no pronation). For other postures, there’s no description given of what the numbers mean.
* Some of the findings:
* On the split keyboard (in its fixed position) the typists had their wrists bent upward more, and some had their left wrists bent inward (radial deviation). For the standard keyboard, they had more wrist pronation and ulnar deviation (wrists bent outward) for obvious reasons.
* Over the two days of testing the split keyboard, typists improved a fair amount, especially when fresh, but at the end of the day were still about 3% slower than on the day with the standard keyboard
* Still though, these typists didn’t seem to have much trouble adapting to the split keyboard (still ANSI/QWERTY layout, etc.)
* Using every type of keyboard, by the end of 4 hours of typing every day, typists reported much more pain/discomfort in back/arms/wrists/hands than at the beginning of the day; there wasn’t really enough data to draw useful comparative conclusions about different types of keyboards here though, other than to report that typing for 4 hour-long blocks of time might be an uncomfortable task regardless of keyboard.
* The 9 typists who used a wrist rest had better typing performance on the split keyboard and more improvement in performance from day 1 to day 2, and reported less arm and shoulder pain.
* * * * * * * * * * * * *
Some things I like about the study: they adjusted the height of the chair/desk to match each participant (at least half of all ergonomics studies don’t do this), they somewhat tried to keep extraneous variables fixed, they reported most of their data in clear tables, they cited previous research.
Some things I don’t like:
* way too small a sample: differences in performance between 9 people who used wrist rests and 9 people who didn’t could be from any number of other causes with such a small group (it would have been nice if they tested the same people both with and without wrist rest)
* much too short a test: it’s hard to fully adapt to new equipment in 2–3 days
* no full data reported for the posture scores, only a few of the averages
* posture scores not based on any standard metric, so the data they do provide are not interpretable by anyone outside the researchers
* no attempt to analyze posture of arms/torso, only wrist/hand position
* no picture or explanation showing how the arm rests or wrist rests were used by any of the typists
* no qualitative or quantitative description of the difference in typing technique between typists
* split and standard keyboard weren’t as similar as they should be for proper comparisons
* no study of the effect of various adjustments to the split keyboard. Split keyboards have at least 3 degrees of freedom of adjustment (tent angle, yaw angle, separation distance) that standard keyboards don’t, in addition to the 3 degrees of freedom on any keyboard (height, distance to the body, and front/back tilt), and they just used a single fixed position for their study
Overall, I don’t find this particular study too enlightening. It finds something I could have told them before: people who are typing on a keyboard with the hands too close together but not angled inward to match forearm length and thus their elbows sticking out to the side a bit or their arms held a ways in front of their bodies are going to get tired shoulders and backs, which can be ameliorated by a wrist rest but not really fixed. People who type on a tilted keyboard with more tilt than warranted for the height of the home row are going to end up with extended wrists. People who type for most of four hours continuously with barely any breaks are going to become fatigued and might experience pain regardless of keyboard.
Random list of ideas about want I want to see in keyboard ergonomics research: Give people an adjustable keyboard and a standard keyboard which are in other respects identical (same switches, same layout, etc.), some substantial training about sitting/typing posture, and expert help adjusting both keyboards until as many of their joints as possible are in as neutral a position possible. Hook up devices which measure tendon/muscle strain, and see if the differences are detectable between setups. Try to record 3D position of joints over time, and report precise objective measurements of posture. Maybe for contrast let the people initially set the keyboards up themselves before any training and see how they set them up and whether they naturally will reduce their level of strain or if expert advice is required. Try putting split keyboards into at least 20 different configurations, to better test the full space of possible adjustments. Measure more than 20 people. Try measuring not only during a few days of a study, but then go back a few months later and see what their new preferences are, and redo the formal tests to see what has changed. Make sure to ask some questions about sleep level, hunger, anxiety, and other recent activities to make sure there are no confounding variables. Measure not only average typing speed over the course of an hour but also more granular typing speed and granular information about errors, and see if there are any patterns to be found there. See if finger motions change at all as typists get fatigued, or if sitting posture starts changing. Record the various typists body/arm/hand measurements, including the range of motion and strength of various joints, to see if that has any effect on typing technique or performance. Analyze different typing techniques of different typists, and see if they can be classified, and if they respond differently to different keyboards. Study the interaction of keyboard design with different pointer devices, with mixed tasks that aren’t 100% typing. Try setting typists up with alternative types of seating, or with standing desks. Give people a few recovery days between intense all-day typing tests. Allow typists to spontaneously change sitting position or other posture whenever they want, and see whether people cycle their positions to give tired muscles a break. Etc.
